Squeeze type power element



Dec. 8, 1959 s. VERNE-r sQuEEzE TYPE POWER ELEMENT Filed April 12, 1956INLET ,.,1 8 M 8 f f 2 o .MJ/f/.f//V/.Y/NJ/,w//VJ/ a# l E. 1 U. E,... ,u.E n, 4 //V/ J///// E M ../o m H nited States Patent Q 2,915,900 SQUEEZETYPE POWER ELEMENT Sergius Vernet, Yellow Springs, Ohio, assignor toAntioch College, Yellow Springs, Ohio, a corporation of h10 ApplicationApril 12, 1956, Serial No. 577,769 2 Claims. (Cl. 73-368.3)

This invention relates to a power element operable by pressure change ina pressuredproducing material. The pressure-producing material may be acontained thermally expansible material as, for example, disclosed inU.S. Patent No. 2,259,846, or the pressure-producing material may be auid introduced from a remote source as illustrated in Fig. 3 of U.S.Patent No. 2,534,497.

Power elements of the instant type include a casing for thepressure-producing material, and a piston slidably mounted in thecasing. Pressure change in the pressureproducing material causes thepiston to move into and out of the casing. A resilient diaphragm, orliner element is provided between the piston and pressure-producingmaterial to prevent iiuid fiow into or out of the power elementinterior.

Objects of the present invention are to provide a power element wherein:

(l) A relatively great piston movement distance is obtained per givensize power element.

(2) The piston movement distance per given pressure change in thepressure-producing material is the same over successive power elementcycles.

' (3) The liner is prevented from wrinkling, working irregularly, orbinding in the power element, as by being pinched or extruded in thejoint between the liner and power element casing.

(4) The liner is readily formed to such precision limits as are requiredto secure the desired piston travel without wrinkling or binding of theliner material.

(5) The piston is accurately guided for straightline movement so as notto be thrown oii its predetermined course and cause binding of theliner.

(6) The piston extends through the element to permit attachment of anoperated device on either end of the piston in accordance with clearanceconsiderations, and desirability of actuating the device in a givendirection by power element pressure increase or decrease.

Other objects of this invention will appear in the following descriptionand appended claims, reference being had to the accompanying drawingsforming a part of this specification wherein like reference charactersdesignate corresponding parts in the several views.

In the drawings:

Fig. 1 is a sectional view through one embodiment of the invention.

Fig. 2 is a sectional view through a liner element e'mployed in the Fig.1 embodiment prior to its assembly on the Fig. l power element shaft.

Before explaining the present invention in detail, it is to beunderstood that the invention is not limited in its application to thedetails of construction and arrangement of parts illustrated in theaccompanying drawings, since the invention is capable of otherembodiments and of being practiced or carried out in various ways. Also,it is to be understood that the phraseology or terminology employedherein is for the purpose of description and not of limitation.

In the drawings there is shown a power element 1 li11- 2 cluding acasing 2. Casing 2 includes a tubular wall 3 and end walls 4 and 5.Se'curemen't of walls 4 and 5 on wall 3 is effected by rolling each ofwall portions 26 from its dotted line position 27 into its full lineposition overlying the adjacent end wall; l l

Walls 4 and 5 are provided with aligned openings 6 and 7 which slidablyreceive a piston `8. Piston 8 includes a first section 9 of uniformdiameter, and a second section 10 of a lesser uniform diameter. Ashoulderforming section 11 is provided between sections 9 and 10. Theangle between shoulder 11 and sections 9 and 10 is preferably abouttwelve degrees.

The upper end 2d of piston 8 is enlarged to form a shoulder 21 forlimiting downward movement of the piston to its illustrated position.Downward movement of the piston is obtained by means of a compressioncoil spring 22 retained between two washers 23 and 24. Each of thewashers is provided with an annular groove or recess 25 adjacent itsouter peripheral edge for correctly seating spring 22 between thewashers. Washer 24 is immovably attached on piston `8, and washer 23 isloosely received on piston y8.

Within power element 1 and surrounding piston 8 is a liner 12,preferably formed of rubber or rubber-like elastic material. Liner 12includes a tubular portion 13 and annular wall portions 1-4 radiatingright angularly from opposite ends of portion 13. Each of wall portions14 includes an annular projection 15 fitting in an annular groove 16 inthe adjacent casing end wall, and a flash edge portion 17 clampinglypositioned between the casing end wall and tubular wall 3. Theconstruction of portions 15, 17 is the same as that of in U.S. PatentNo. 2,636,776.

Prior to its insertion on piston 8 liner 12 takes the Fig. 2 congurationwherein internal dimension (a) is the same as the diameter of pistonsection 10. As a result the tubular portion 13 of the liner must undergoa stretching action in order to be iitted onto piston section 9. Thestretched condition of tubular portion 13 causes it to tightly hug thepiston so as to prevent the occurrence of any wrinkling action duringmovement of piston 8.

Liner 12 effectively isolates and seals piston 8 (and its joint with endwalls material 18. Material 18 is in the illustrated embodiment athermally expansible material, as for example that illustrated in U.S.Patent No. 2,259,846. Material 18 may however be a pressure fluidintroduced from a remote source as illustrated in Fig. 3 of U.S. PatentNo. 2,534,497. The presence of liner 12 insures that no uid will enteror leave the power element interior from or to ambient atmosphere 19during pressure change in mal terial 18.

During pressure increase in material 18, as during temperature increasein ambient atmosphere 19, the pressure material acts against shoulder 11to force piston 8 upwardly against the action of spring 22. Duringpressure decrease in material 18 (occurring during temperature decreasein atmosphere 19) spring 22 returns piston 8 downwardly to itsillustrated position.

Due to the fact that piston 8 extends completely through the powerelement casing, liner 12 always hugs the piston. This hugging action isenhanced by the fact that liner 12 initially has an internal diameter(a) less than the diameter of section 9. Since the liner is at all timeshugging the piston it can never wrinkle during piston movement.

Certain prior art power elements include a piston having a rounded endportion extended into a cup-shaped liner or diaphragm within the powerelement interior. This type of power element gives comparatively largepiston travel distances per power element size but the pisportions 72,73

ton speed and movement distance tends to be variable or 4 and 5) frompressure-producingv result the liner must wrinkle.

erratic for successive power element cycles. Thiserratic operation isbelieved to be due to a wrinkling of the liner during piston movement.This wrinkling is believed to `result from the fact that the cup typeliner is difficult to mold to the precision limits necessary to maintainall portions of the liner against the piston throughout the entirepiston movement. It is also believed that the wrinlcling may be in partdue to the fact that the lower r portion of the liner (adjacent therounded end of the piston) has too much internal surface area tocollapse downv tion wherein shoulder 11 is just below the level ofwasher 28. Due to the guiding action of opening 7 the piston is at alltimes guided for straightline movement into and out of the power elementcasing.

During pressure increase in material 18 piston section 10 is pulledtoward the power element and piston section Z0 is pushed away from thepower element. VAs a result a valve element (or otherdevice to beactuated)` may be secured to either of piston sections lil or 20accordingly as it may be desired to give a .pull or push -to theactuated ldevice during pressure increase in material `18.

Conventional power elements (wherein the pistol-in does not extendentirely through the power element) have not element the piston isaccuratelyguided for straightline f movement throughout the entire range`of piston movement. Prior art power elements (wherein the pistonextends only partially through the power element) d o not accuratelyguide the piston as it nears its outermost position. This is dueto thefact that the length of the available guide surface is reduced as thepiston nears its outermost position. The guide surface is usuallyprovided by an elongated sleeve extending from the power element casing,and the guide surface can of course be lengthened by lengthening thesleeve. overall length of the power element, and for many applicationsthe resultant power element would be too long to be accommodated in theavailable space.

It will be noted-that the guide surfaces provided by openings 6 and 7are spaced apartv and operable in all positionsof piston 8. Inconventional constructions the piston guide is one continuous surface.of any point along the continuous surface or any uneven pressuredistributionon the piston may alter the path of the piston. Anyalteration of o r change in the piston' movement path may causelocalized portions of the liner to be squeezed or extruded into thejoint between the liner and guide surface soas to be wrinkled and cutaway from the liner body.` VSuch action may intime result in failure ofthe liner and loss of power element calibration.'

In theFig. l construction the spaced guide surfaces provided by openingso and 7 insure straightline piston movement throughout the entire pistontravel, and considerably reduce the possibility of any of the linermaterial being. extruded into the joint between the piston and guidesurfaces. This anti-extrusion feature maybe enhanced by a `washer 28formed of polytetrailuorethylene or other low friction, resilientplastic material. The jointbetweenrend wall 5 and piston section 10 mayalso be provided with an anti-extmsion washer if .foundnecessary Asshown in Fig. l anti-extrusion protection is offered by theconfiguration of casing Tend wall 5, said end wall'being vformed with aninternal annular extension 34) projecting inwardly to define alinercngaging surface which is rounded adjacent its juncture withopening 7 and which slopes at an acute angle-away from the` surface ofpiston section dt'whereby to cooperate with the cohesiveness of theliner material in deflecting the liner away from the joint between'thepistonand wall opening 7.

l t will be noted that the entire central portion of'casing 2 isoccupied by piston 8 (because the' piston extends completely through thecasing). Asa' result all of thermally cxpansibie material 16 isdisplaced outwardly away from the casing central portion.' BydisplacingallV of material llt;v toward the casing outer wall the material willlexpand and contractmore quickly in response 'to-temperaturechange in;atmosphere 1 9. The power element is thereby enabled to more quicklyfollow the' condition' of atmosphere 19. Casing 2 can be `made largeenough towh'oldV a quantity of material 18 suiiicient for pushing piston8 upwardly from its illustrated position to a posi- This howeverincreasesv the A n irregularity enabled the user-.to secure Vay push orpull piston action. Considerations such as power element size andplacement in confined locations sometimes make it desirable to be ableto choose betweeny a push or pull piston action. v n In the illustratedconstruction the spring pushes the piston into the power element duringpressure decrease in; material l8. Itis contemplated however that thespringj could pull the piston into the power element, in which; casesection 20 could be provided with an extension and encircling springmechanism.

Ivclaim: f 1. A powerk element comprising a casing including av tubularwall and two opposed walls closing the ends of.` the tubular wall; saidend walls having aligned openingsl therethrough; pressure-producingmaterial within the casing; a'pistonV extending throughY the alingedopenings; saidland joined to said first section, said second sectionhaving a different diameter than'the first section, la shoulder. beingformedA at their juncture; an elastic tubular liner of material subjectto extrusion engageably surrounding the piston; said liner havingannular wall portions extending angularly from itsV ends and lyingagainst interior surfaces ofthe end walls so as to isolate thepressure-producing material from the joints between the piston and 'endwalls; said liner being formed throughout the major portion of itslength with'an internal diameter substantially the same as that of thesmallest diameter pistonsection, whereby to be put in a non-wrinkablecondition when engaged with the largestv diameter piston section andsmallest diameterV piston section, one of said end walls having anannular recess formed inthe inner surface` thereof and around theopenings therethrough; a` washer of low friction, resilient, plasticmaterial seated in said recess, whereby to prevent extrusion of theliner material into the joint between the piston and opening;` the otherend wall having an internal annular extension projecting inwardlyadjacent the end wall opening to dene a linerengaging surface which isrounded at the juncture with the opening and which slopes therefrom atan acute anglev awayfrom the piston surface, whereby to cooperate withthe cohesiveness of the liner material in deflecting the liner away fromthe joint between thepiston and other end wall opening. i

2. A power element comprising a casing including a tubular wall and twoopposed walls closing the endsof the tubular walls; said end wallshavingj'aligned openings therethrough; pressure. producing materialwithin, the casingfa pistonV extending through the alignedopenin'gs;said 'pistonincluding a first luniform' diameterV sectionY extendingthrough one of the openings, and a`second uniform' diameter sectionextending through the .othery opening andrjoined to said rst section,said secondsection having adilferent'diarneter than the first section,`

having annular wall portions extending angularlyfroml itsV lendsandlying against interior surfacesV of the `end walls so as to isolatethe pressure producing material from the joints between the pistons andend walls; said liner being formed throughout the major portion of itslength with an internal diameter substantially the same as that of itssmallest diameter piston section, whereby to be put in a non-wrinkablecondition when engaged with the largest diameter piston section andsmallest diameter piston section; one of said end walls having aninternal annular extension projecting inwardly adjacent the end wallopening to define a liner-engaging surface which is rounded at thejuncture with the opening and which slopes therefrom at an acute angleaway from the piston surface, whereby to cooperate with the cohesivenessof the liner material in deliecting the liner away from the jointbetween the piston and one end wall opening.

References Cited in the le of this patent UNITED STATES PATENTS2,208,149 Vernet July 16, 1940 2,494,598 Waring Ian. 17, 1950 2,806,375Wood Sept. 17, 1957 FOREIGN PATENTS 1,100,683 France Apr. 6, 19551,125,435 France July 16, 1956 OTHER REFERENCES Bulletin OB-1152,published by the United States Gasket Company of Camden, New Jersey, 8pages, only pages 1-4 needed. Received in the Patent Oce February 3,1956.

